The subject invention generally relates to thermal ink jet printheads, and is directed more particularly to a thin film thermal ink jet printhead having a compound ink feed slot.
Thin film thermal ink jet printheads commonly comprise a substrate such as silicon on which are formed various layers that form thin film ink firing resistors, interconnections between the ink firing resistors and external contacts of the printhead, an ink barrier that is configured to define ink containing regions including ink containing chambers that are disposed over associated ink firing resistors, and a nozzle plate having nozzles attached to the ink barrier. The various layers of a thin film thermal ink jet printhead are typically formed by thin film photolithographic masking and etching techniques. The ink barrier may be formed using photolithography to pattern a suitable material. An electroformed metal nozzle plate is then laminated to the ink barrier layer.
A known arrangement for feeding ink into the ink containing chambers includes the use of a relatively large ink feed slot formed through the substrate whereby ink flows, for example pursuant to capillary action, from the lower side of the substrate to the ink chambers. An important consideration with the use of a large ink feed slot formed through the substrate is the reduction in strength of the substrate resulting from the formation of the large ink feed slot. Thus, mechanical fragility is a controlling factor in determining the size of the substrate, rather than the intended functionality, which results in greater cost due to the larger substrate. Moreover, manufacturing yield may decrease when substrate size is close to the minimum limit.